Insights into the influences of sensory experience and serotonin on multisensory processing in the superior colliculus

Abstract

The ability to integrate information across the senses is vital for coherent perception of and interaction with the surrounding world. In the mammalian brain, the superior colliculus (SC) is critical for this multisensory processing to occur. Much is known regarding the organization and function of neurons within the SC, including the necessity of normal sensory experience for proper development of these neurons, influence of modulatory neurotransmitter systems, and how these specific neurons are involved in multisensory integrative processing. However, open questions regarding how neurotransmitter systems and developmental parameters are involved in multisensory processing in adulthood remain. Previous work has shown that sensory experience throughout development is essential for proper multisensory integrative capacity of SC neurons. Here, it is established that this normal sensory experience requirement is maintained throughout a lifetime; perturbation of visual experience in adulthood also affects multisensory integrative capacities of SC neurons. In addition, studies detailed here sought to determine the role of the serotonergic (5-HT) system in multisensory processing occurring within the SC. Through electrophysiological and pharmacological methods, a modulatory role of the 5-HT system was demonstrated, as alterations in the serotonergic signaling system within the SC affected responsivity, receptive field characteristics and integrative capacities of multisensory neurons. These studies help to further our knowledge and understanding of the mechanisms at work in the SC in order to produce and maintain proper multisensory processing capabilities.